Hi all, I am looking for more information about the issue of galvanic corrosion. I've been asking the conservators and they have a huge range of reactions to the issue. Some sound as though the mount will implode if there is a steel D-ring attached to the brass mount others saying that as long as it's not being installed in a swamp it will be fine. Does anyone have information about this? Thoughts about what to do? Are certain alloys better or worse than others? I am currently working on a group of brass mounts with brass posts that will sleeve into steel tube and plates to the wall. One conservator suggested a sleeve of teflon over the brass, though the set screw might pierce the teflon and how secure is that really? Maybe sleeve of another type of metal? Thanks for your thoughts
You could coat the brass rod with B-72 and use nylon tipped set screws. Or could you use stainless steel or brass tube? We often make or own brass sockets on the metal lathe.
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There is info on galvanic corrosion on p. 28-30 of Lyndsie Selwyn's book Metals and Corrosion: A Handbook for the Conservation Professional, Canadian Conservation Institute 2004 , described here
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I don’t think I’d spend too much time worrying about galvanic corrosion in a normal museum environment. I feel that without a high moisture level and a way of completing a circuit, you shouldn’t develop the potential for the exchange of ions that is galvanic corrosion. Unless you have an electrolyte to help move the process along there isn’t going to be much of a tendency to corrode. I’ve used steel sockets with brass posts for years and have never seen any sign of corrosion where the two join.
The one place that does merit some attention is to not leave excess flux present after silver brazing a joint on a metal mount. The flux can be hygroscopic and can lead to a certain amount of surface corrosion. In a worst-case scenario, it could lead to a post and socket either loosening, or freezing together. That said, it tends to be more of a mess than a structural hazard.
I say these things both as a long-time mountmaker who uses metals in combinations on a regular basis, and as a former boat owner. I did get to know the realities of galvanic corrosion while living on a wooden sloop on Puget Sound in Seattle. In that setting they can definitely be a serious problem. Please feel free to get in touch directly if you’d like to talk about this further.
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I forgot to add that the Wikipedia entry on Galvanic Corrosion is quite a good explanation of the process. I encourage you to give it a look.